Apparatus for mixing



2, 1958 M. M. BEAN 2,847,195

, APPARATUS FOR MIXING Filed Dec. 2, 1953 2 Sheets-Sheet 1 HOV Fig.1

INVENTOR M08675 MB'A/V BY Cu/IJIAJWJUZQJJ ATTO R N EYS Aug. 12, 1958 M. M. BEAN APPARATUS FOR MIXING 2 Sheets-Sheet 2 Filed Dec. 2, 1953 Fig. 2

'INVEN'TOR MOBQ/S M BEA/V CMMOMLLJJ Fig.5

ATTORNEYS United States Patent Ofitice Bean and Company, Yellow Springs, Ohio, a corporation of Ohio Application December 2, 1953, Serial No. 395,737 '18 Claims. (Cl. 259-) This invention relates to apparatus for thoroughly mixmg dry and liquid materials to form a soft, smooth mix,

and for delivering the resulting mix through a convenient conduit. More particularly, the invention relates to the separation and injection of slurries .of settable materials such as plaster of Paris and the like.

In the preparation of such mixtures, experienced in so blending dry and wet constituents as to insure a smooth, uniform mixture free from air bubbles. Another diificulty is to reach such smooth uniform consistency before the binder has set up and thereafter to expel the mix from the apparatus before it has set. Where this problem has been met by using a slow setting mix to give time for the mixing operation plus necessary holding in transit before it is molded, production has been unduly delayed with serious increase in the capital tied up in mold equipment (mold is used broadly herein to include patterns, etc., as well as external molds).

The present invention aims to provide improved apparatus for effecting a thorough mixing of dry and wet constituents into a slurry and holding the slurry ready for molding during the variable delays normally encoundifiiculty has been tered in manufacturing and yet to supply the mix on demand in condition for prompt setting up in a mold.

An important feature of the invention is the simple mixing device which not only effects the mixing of the dry and wet constituents of the slurry, but also subjects the solid particles of the slurry to a rubbing and squeezing operation. This results both in improving the uniformity of the mixture and at the same time in driving out any gases.

Another important feature of the invention is the novel ejection means and its arrangement in the apparatus.

It is important also that all parts which contact the mix are so simple. and accessible that an effective washing of all operating parts can be effected by a simple flushing operation.

Further important features are the maintenance of a controlled head on the slurry and automatic supply of materials to replace mix withdrawn from the machine. A novel construction of the ejector, particularly of the ejector piston, and the use of the ejector piston as a valve, are also important features.

Another important feature is that the cycling of the ejector pump and the inflow of materials are independent of time and flow but responsive to withdrawal of the mix. Especially important is that uniform ejection pressure is effective at all times except momentarily during retraction of the ejector piston.

Other objects, important features and advantages of the invention which have not specifically been pointed out hereinabove will appear when the following description and claims are considered in connection with the accompanying drawings, in which:

Figure 1 is a side elevation of mixing and ejecting apparatus embodying the present invention, certain appurtenant parts being shown diagrammatically, certain parts by a relay and solenoid valve,

2,847,195 Patented Aug. 12, 1958 in phantom and part of the heat exchanger being broken away;

Figure 2 is a view, on enlarged scale, mainly in vertical section but partly in elevation, of the mixing chamber and mixing mechanism together with the ejection pump connected therewith;

Figure 3 is a similarly enlarged sectional detail showing the ejector piston at the lower end of its stroke and with its expansible gland contacting the cylinder wall to prevent by-passing of the slurry around the piston;

Figure 4 is a sectional view of a modification in which a fixed ring gear engages pinions on the several roller shafts to positively determine the rotation speed of the mixing rollers;

Figure 5 is a fragmentary cross-sectional view similar Figure 3 showing a modified expansible piston.

In the embodiment of the invention herein illustrated, a suitable frame 8 is provided for supporting the operating parts of the mechanism. Advantageously, this is a conventional type with an upright pillar mounted on a base provided with casters for full mobility. In the drawings as here shown, this frame 8 is partially broken away for clear showing of the operating parts.

The device embodying my invention comprises a mixing chamber 2, in which the constituents of a slurry to be formed are mixed, and mixing rollers 10 operating in said mixing chamber to crush and rub the constituents of the slurry against the chamber wall. In this embodiment, mixing chamber 2 is shown as a casting carried by a bracket 6 of the frame 8. The mixing chamber is funnel-shaped with the bottom part 11 of its walls at a greater angle to its axis than along their major depth.

The rollers 10 are mounted in bearings in a yoke 12 which has a hub 14 rotated in bearing 16 supported on bracket 20. This is also attached to the vertical frame member 8. The belt 22 drives the hub 14 from pulley 24 on a gear reducer 26 driven by a motor 28.

As shown, the bearings for each of the rollers 10 are eccentrically mounted in a cylinder 36 fitted in the yoke 12. These cylinders can be rotated by a tool inserted in one of a plurality of holes 38 and thus the rollers 10 can be adjusted radially to bring them into the desired tangential contact with the inner surface of the mixing chamber 2. Each cylinder 36 can be locked in its adjusted position by means of a set screw 40.

The bracket 26 as shown has an open center 42 through which extends conduits for the materials to be mixed. Proportioned feed of these materials is supplied, the dry materials through the tube 44 and the liquid through the spray ring 46 and pipe 48. The proportioning of these materials is advantageously effected automatically by apparatus such as that disclosed in my said Patent No. 2,574,238. However, in order to avoid repeating here the extensive description and drawings of the proportioning apparatus as given in my patent, I have shown diagrammatically, in Figure 1, an ordinary proportioning feeder 49 which measures out the powder feed in response to or in conjunction with flow of the liquid, the liquid, in turn or conjointly, being controlled,

from the feeler circuit including probe 52. As the level of the slurry in chamber 2 rises to that shown at 50, electric probe 52 completes a circuit to actuate a solenoid valve controlling the flow of liquid; and, with the flow of liquid stopped, no further dry material can be fed by the proportioning device until 3. pipes 72 of the patent and distributor 74- become pipe 48 and distributor 46 above described. The feeding and proportioning apparatus of Figures 1-7, 9-12 and 21, as wellas the mounting anddeliverymeans of Figures 229, can be used substantially as shown in said patent. This combinationthen wouldoperate as follows:

As the level of the slurry ,in chamber 2 rises to that shown at 50, electric probe 52 energizes a relay which in turnencrgizes the timer, which shuts off a motor ,for a definite time interval allowing the slurry level 50 to drop a short distance, depending upon the rate of discharge from nozzle 161. This motor drives the plaster meter wheel and the water meter pump geared together to maintain a uniform consistency, and at the expiration of the time interval the motor turns on and the liquid level approaches the electric probe 52.

i This mixing chamber as above described makes possible the satisfactory operation atmaximum demand, thus requiring very little storage of the mixed material, which would have to be wasted when the production was interrupted for more than arfew minutes.

The cylindrical rollers 10 travelling over the conical surface lag behind said surface at the top and turn faster than a rolling speed at the bottom. Thus, a rubbing and smearing action highly effective for mixing the powder into the liquid is achieved. The drag forward on the top of each roller is balanced against the drag back on the bottom of the roller. Only a section near the center of the roller actually rolls on the conical surface of the chamber without slippage. The conical ends of the rollers extending to and even over the outlet from the mixing chamber and rotating at relatively high speed, create a final turbulence in the exit and assure that all material before leaving the mixing chamber will have been rubbed .between the rollers and the chamber wall.

The discharge .end of the mixing chamber 2 merges into a cylinder 54 .provided with an ejector piston 70. The cylinder 54 is secured by a clamping ring 59 bolted over flange 5,6 and onto thebottom of the chamber 2.

A coupling 66 shown, also in Figure 2, connects the cylinder 54 to the discharge line, including pipes 68, 148 and 160. The inside of this coupling is smooth for streamline flow and is contoured similarly to the bottom of piston 70 (see Figure 3).

The probe 69 extending down from piston 70 aids in keeping pipe 68 open.

The piston 70 comprises essentially a gland, here shown as a ring 71 of rubber-like material, advantageously a thick-walled tube of pure gum vulcanized rubber or any elastomer composition sufiiciently hard and strong and tough to resist the high fluid pressures encountered and the repeated extrusion and retraction from, and between -a support portion .here shown as a flange 74 and apresser foot here shown as a nut 78. In themodified piston shown in Figure 3, a toroidal ring 71a like an automobile tire is used, with its inner rims clamped respectively to the flange 74a and the nut 78a. In either case, when the gland is squeezed, it extrudes laterally to the external shape shown in Figure 3. When the flange 74 and nut 78 are moved apart, the gland is extended longitudinally and retracted radially to the shape shown in Figure 3, in which the slurry'may by-pass the piston. As

shown in greater detail in Figure 3, lateral extrusion and retraction of the piston are effected by the relative movement of the hollow rod .72 and the center rod 76.

Instead of mechanically-expanding the piston ring 71, as :shown in Figures 2 and 3, this function can be performed pneumatically or hydraulically, e. g., by-using for ring 71b an inflatable annular tube-as shown in Figure -5 with an opening at 79 connecting it through the bore of tubular rod 72b, to the hose 140. The ring 71b -'is cemented to the rim of flange member 74b, particularly around the hole 79.

Great care must be exercised in design of piston 70 to keep from introducing air between 70 and 71, or to prevent leaks around tube 71a or 71b.

Rod 72 is also flanged :at its upper end and rigidly connected to the bottom of the cylinder 82, and rod 76 is connected to piston 80 in the cylinder 82, so that fluid pressure in the cylinder compresses and extrudes ring 71. A spring 84 in this-cylinder urges piston 80 and rod 76 downward relative -,to.ro,d '72, to retract ring 71 to the form shown in Figure 2.

The cylinder 82 is moved bodily by the piston rod 86 driven by piston 88 in cylinder 90 counted on bracket 92 of frame 8. Rod 86 is threaded for adjustment and provided with lock nuts, to control the amount of squeeze on piston ring 71 so as to assure a tight fit in cylinder 54 without excessive friction.

A three way solenoid valve 98 operates to introduce air pressure into the cylinder 82 to extrude ring 71 when its solenoid is energizedandto .vent air from the cylinder to retract the gland when the-solenoidis released.

A 'four-waysolenoid valve-102 introduces air-pressure above piston 88 and vents the space below the piston when its solenoid is energized, thus urging piston 70 down into cylinder 54 and imposing asuitable head on the slurry for delivery from the apparatus; when the solenoid is released, valve 102 vents the top and introduces pressure below the piston 88 to lift piston 70. A limit switch 106, normally closed and having one contact positioned to be engaged by finger 108 on cylinder 82,'li'mits theinjection stroke Qfthe piston 70 by breaking the energizing circuit of valve102.

A controlling switch 116 as shown may be put into any of three positions: run, off, and start. When it is in .the start or the run position, it energizes the motor 28, e. g. by conventional circuit connections (not shown).

In the start position this switch makes connections around the relay 123, i. e., the circuit of valve 98 is closed independently of the timer 112; whereas in the run position, theswitch connects both solenoid valves 102 and 98 through contacts '126 and 128 of relay 123 thus making them subject-to control by the timer. If this switch 1,16'were left in the startfposition, the piston 70 would not be effectively retracted, but would serve only as a stopper. If the switch 116 were left always in the run" position, it would not operate valve 98 until relay 123 had received-a pulse from the timer; and then pumping would start. The start position of switch 116 provides for operation of fiuid motor 8 l-$2 to stopper chamber 2 before the timer 112 is started.

An electronic (or other available) pulse timer 112. operated 'from the feed line through the wires 114 and 118 and the. hand operated switch 122, closes the circuit to the relays 123 for short pulses at time intervals predetermined by the setting of the timer. Contacts 12,6.and 128 are provided on relay 123 to be closed by its armature; and the connections 13.0, 13-2 and the normally closed limit switch 106 provide a holding circuit .for the. windingof the relay so that, once closed, itremains closed through this holding circuit until switch 106 is opened. Once opened, the relay remains open until a pulse from the timer 112 re-energizes it.

Contact v126 closes .the. above mentioned holding circuit forrelay- 123 and the contact 128 closes circuits to the solenoid valves 98 and .102. At first, the energizing circuit for relay 123 is through the connection 124, timer 112, contacts 122; but when relay 123 is operated the circuit is through connection 130, limit switch 106 and connection 132.

,Air-fiow control valves. are provided at 134 and 136 to regulate the speed of piston 88 and ejector piston 70 connected to it. An air.contro1 valve 138 similarly regulates the speed at which the ejector piston '70 is expanded or contracted by movement of piston 80. Air line 140 is a flexible hose or pipe to accommodate vertical movement of the cylinder 82.

In Figure 4 of the drawings is shown a modification of the embodiment shown in Figures 1 to 3 wherein the rollers 10!! are positively rotated by bevel gears 141 which mesh with the fixed ring gear 142 mounted on bracket 20a so that the rotation of the yoke 12 drives the pinion 141 over the ring gear 142 and thus rotates each of the rollers 10a. The ring gear may be external or internal. By the proportioning selected for the respective diameters of the pinion gears 141 and the ring gear 142, any desired speed of rotation may be given to the rollers 10a and any desired rubbing action attained.

In the operation of this mechanism, switch 116 is moved to its start position, whereupon the motor 28 is started and solenoid valve 98 is energized to cause the expansion of the injector piston 70. This closes the outlet from the mixing chamber 2.

The liquid and dry materials to be mixed are then introduced by the automatic proportioning device 49 and through the conduit 44 and a spray head 46 respectively. The cylindrical rollers 10 meanwhile have been started in rotation by motor 28, driving through belts 22. The rollers operate against the inner surface of the mixing chamber 2 with both a rolling action to squeeze out any air bubbles, a crushing action to break up any lumps of the powder, and a rubbing action against the inner surface of the chamber to thoroughly wet the surface of every particle and produce uniform slurry. By reason of the fact that the upper ends of the roller 10 travel around the longer circumference of the top of the funnelshaped chamber 2 while their lower ends traverse a shorter path at the bottom of the chamber, the rubbing action varies both in direction and degree. The frustoconical end 144 or" the rollers 10 and the fitting conical bottom 11 of the chamber permits the rolling, rubbing and crushing action to extend substantially to the outlet of the chamber 2 and thus prevents settling out of solids and retards solidification of the slurry when the discharge is shut oil.

The introduction of liquid and dry constituents and the mixing continue until the material fills the chamber 2 to the level 50, when it contacts the electrical probe 52 to stop further introduction of the constituents.

When the chamber 2 is thus filled, the switch 116 is moved from start position to run position and the switch 122 is closed to start the timer 112. Removing the switch 116 to the run position releases the solenoid valve 98 permitting exhaust from the cylinder 82 to allow the piston 80 to return and retract the gland 71. As timer 112 moves, it soon sends a pulse to the relay 123. After each pulse, the relay 123 is held energized by the holding circuit through contacts 126, connections 130, 132 and limit switch 106 until limit switch 1% is opened. With contacts 128 closed, both valves 98 and 102 are operated so that piston 80 is moved up, expanding piston 70 to a tight fit in cylinder 54, and piston 88 is driven down causing piston 71) to move down and eject the slurry from cylinder 54 through the line 68, 148 and 160.

At the end of this stroke, a projection 108 on cylinder 82 strikes and opens limit switch 106, which drops relay 123; and solenoids 98 and 102 are thus de-energized which reverses both solenoid valves to retract the piston gland 71 and lift the piston 70.

The liquid supplied through the pipe 48 and spray head 46 is advantageously cold enough to substantially retard the setting of the slurry. In the case of plaster of Paris, I thus use water at a temperature about to 20 C. To the same end, the chamber and/or cylinder 54 may be jacketed or provided with a cooling coil and a refrigerant fluid circulated to chill the mix to that range. It is desirable, however, that the slurry set rapidly when it has been introduced into the mold. In the illustrative embodiment of the invention, therefore, a heater 146 is provided so that the slurry is delivered from the discharge nozzle into the mold in a condition ready for quick'setting, advantageously 50-65 C; The required temperature is automatically maintained by supplying to a steam jacket 146 saturated steam at a pressure corresponding to a slightly higher temperature, e. g., of a pressure about 2 to 30 p. s. i. above atmospheric. The condensate drains from the low point of this jacket through a pipe 152 and a thermostatic trap 154 and the discharge pipe 156. A steam gauge 158 shows the pressure and/or temperature.' A shut-oif valve 150 provides for stopping the heat or reducing the rate of heating, if the discharge is to be cut oif for any substantial time or unduly retarded.

A flexible tube 160 provided with a nozzle 161 receives the slurry from the tube 148 and enables the operator to deliver it at the desired points in the molds, etc.

The slurry is delivered from the nozzle 161 at a temperature near that of its maximum setting speed and in a stream of about 4 to /2" diameter or larger (the particular nozzle being chosen to give the most advantageeous size stream for filling the plaster into the detail of the particular mold). The velocity of the stream, which is regulated by the air pressure supplied through the valve 192, is adapted to drive the plaster into the detail by its momentum but Without whipping it up so as to entrain any air. Thus, in one preferred embodiment the air supplied by the piston keeps a head of lbs. per square inch on the slurry.

As one example: A dry mix containing 42% gypsum cement, 47% fine sand, 8% talc and 3% terra alba was mixed with water at 5 C. to the consistency of soft mud or slurry. This could be held safely in the machine for four minutes and it would take about 15 minutes thereafter to set. The chamber 2 was, therefore, designed to hold only enough of the mix for about a two-minute supply for normal use. After this mix had been pumped through the heater 146, its temperature was raised to 50 C. and the mix was then set in 2.8 minutes, thus allowing adequate time for filling it into the mold and for it to flow and form itself into the detail of the mold.

As above pointed out, one of the great advantages of this invention is that slurries such as gypsum plaster can be made and a supply kept at a temperature so low that setting will not occur in the machine and yet will occur promptly after delivery. Because the piston and the mixing device are immersed in the slurry throughout the operation of the apparatus and operate through the open upper surface of the material in the hopper without glands or other devices which could leak air below the surface of the slurry, the danger of introducing air bubbles is substantially entirely eliminated and the mechanical design of the apparatus is greatly simplified by the avoidance of the need for stuifing boxes or glands to control such air leakage into the apparatus.

When use of the apparatus is to be discontinued, the feed is cut off and pumping continued until the hopper is substantially emptied.

Water for flushing out the apparatus is run in at 166. This serves to wash out the mixing hopper 2 and to clean the rollers 15) and piston 70 and all parts with which the slurry has been in contact. By leaving the apparatus running while the flushing water is running in and through the apparatus, pump 70 and rollers 10 serve to agitate the water and to give it relatively high velocity along the surfaces which need to be washed and thus facilitate the cleaning of all parts which have been covered by the plaster. Rod 69 also helps in assuring a thorough washing of the pipe 68.

I claim:

1. Apparatus for mixing a quick setting slurry and promptly ejecting it under pressure which comprises a delivery conduit, a mixing chamber with an inlet for ingredients of said slurry and an outlet opening into said conduit at a position remote from said inlet, means for mixing ingredients of a slurry in said chamber between said inlet and said outlet and continually rubbing the mixture along the surfaces ofthe chamber and moving it toward and away from said surfaces during its flow toward said outlet, and means operating in the flow of said mixture from the chamber for ejecting the slurry from thechamber through, and out of the end of, said conduit, whereby said ejecting means is continually scrubbed by the flowing slurry, 'said chamber, outlet and delivery conduit presenting substantially continuous surfaces surrounding a flow path for delivery of the slurry whereby the apparatus is free from substantial delay pockets into-which slurry could escape from the flow long enough to set.

2. Apparatus as defined in claim 1 in which the mixing chamber is of funnel form, an ejector chamber extends coaxially downward from the discharge outlet from the funnel and the ejector means comprises a piston expansible and contractible and a piston rod connected thereto and extending upward through the slurry.

,3. Apparatus as defined in claim 2 in which the piston is centrally positioned in the ejector chamber to reciprocate therein, having a sliding fit when expanded and substantial clearance when contracted, and the apparatus includes means for reciprocating the piston and means for expanding it for the ejection stroke and contracting it for the return stroke.

4. Apparatus for supplying slurry as defined in claim 2 in which the ejector chamber extends axially downward from the mixing chamber and the piston rod extends upward through the mixing chamber, whereby the piston is submergedin the slurry.

5. Apparatus for supplying slurry as defined in claim 4 in which the mixing chamber is funnel-shaped and a cylindrical ejector chamber extends coaxially downward from the discharge end of the funnel.

6. Apparatus for supplying a freshly mixed slurry of the type comprising in combination a mixing chamber having mixing means therein, an ejector chamber communicating with said mixing chamber into which the slurry flows from said mixing chamber, a piston reciprocable in said ejector chamber, means for opening a passageway for the slurry in said ejector chamber beside said piston during the retraction stroke of the piston and closing said passageway during the discharge stroke, and means for reciprocating said piston,which is characterized by said reciprocating means comprising means for resiliently exerting a substantially steady force on the piston, whereby the pressure on the slurry is substantially constant from the beginning to the end of its stroke, regardless of the rate of discharge, means for reversing the force on the piston responsive -to eompletion of the stroke, and means responsive to the completion of the retraction stroke for again reversing said force for a new discharge stroke.

7. Apparatus as defined in claim 6 in which the piston is expansible and contractible and the piston reciproeating means include a piston rod and the means for opening and closing the bypass comprises means movable relatively the piston rod for effecting an expansion of said piston byrelative movement therebetween.

8. Apparatus for supplying-slurry as defined in claim 7 in which the piston reciprocating means and the means for expanding and contracting the piston comprise two direct-connected, slow expansion fluid pressure motors.

9. Apparatus as defined in claim 8 in which the piston comprises an expansible ring, one edge connected to a tube and its other edge connected to a rod movable longitudinally within said tube, and the fluid pressure motor means for expanding the piston is connected .between said rod and tube-to move them in opposite directions to stretch said ring to attenuate it by movement in one direction and to compress it and bulge it out toward the wall of the ejector chamber by reversed movement.

1.0. A pump comprising an impeller chamber having inletand discharge ports at opposite ends thereof, a

piston therein which includes-a support portion subit stantially smaller in cross section than the chamber and a resilient piston gland supported thereby and expansible to close the peripheral clearance around the piston and contractible to clearva substantial space for by-pass of fluid around the piston, means for moving said piston back and forth in the chamber, and means for retracting the resilient gland when the piston is near the discharge end of its travel andexpanding said gland near the opposite end of its travel.

11. A pump as defined in claim 10 in which the piston gland is a resiliently extrudable material engaged on the support portion of the piston and the means for expanding and retracting the gland comprises a compression foot on the opposite side of said piston gland from the support portion of the piston whereby the piston gland may be compressed between the support portion and the compression foot and extruded into engagement with the sides of the impeller chamber and released to retract away from the walls to open a bypass space.

12. A pump as defined in claim 11 in which the means for moving the piston comprises a piston rod connected thereto at one end and a fluid pressure motor connected to the rod at its other end, and the means for expanding and retracting the piston gland comprises a second fluid pressure motor connected between the piston support portion and the compression foot for extruding the piston gland.

13. A pump as defined in claim 12 in which a hopper is connected above the inlet port, the means for expanding the piston gland comprises a rod extending parallel to the piston rod and both extend through the inlet port and above a liquid level in the hopper and the second fluid pressure motor is connected between said rods above said liquid level, and the first fluid pressure motor-is conneeted to the piston rod above said liquid level.

14. A pump as defined-in claim 10 in which the means for moving the piston comprises means connected to the piston for exerting a steady downward pressure thereon substantially independent of its movement and means for retracting the pistonin response to action of a part connected to the piston at the end of its stroke.

15. Apparatus for mixing slurry which comprises a mixing chamber of an upright funnel shape having sloping sides and a discharge passage from an end thereof and mixing means in said chamber comprising a roller mounted to rotate about its own axis and to revolve about the funnel axis, said roller having a surface corresponding substantially to a surface of revolution substantially tangential withthe funnel surface and of diameter substantially less than half the corresponding diameter of the chamber, whereby to leave within the annular path of said rollers a substantial reservoir for the materials being mixed, and means for revolving said roller about said funnel axis.

16. Apparatus as defined in claim 15 in which the mixing means include a substantially cylindrical roller and rotatably supported tangential with the funnel wall in a yoke revolvable about the funnel axis.

I7. Apparatus for mixing slurry which comprises a mixing chamber'of an upright funnel shape having sloping sides and a central coaxial discharge passage extending from the bottom thereof, and mixing means in said chamber comprising a roller mounted to rotate about its own axis and to revolve about the axis of the funnel, said roller having a surface corresponding substantially to a surface of revolution substantially tangential to, and its generatrix coinciding with that of, the inner funnel surface, and means for revolving said roller about said funnel axis, in which the angle of inclination between the side wall of the funnel and its axis is greater at the lower end of the funnel and the roller is provided with a conical surface at its lower end substantially tangential with the said funnel surface of greater inclination.

18. Apparatus for mixing slurry which comprises a mixing chamber of an upright funnel shape having sloping sides and a discharge passage from one end thereof and mixing means in said chamber comprising a roller mounted to rotate about its own axis and to revolve about the funnel axis, said roller having a surface corresponding substantially to a surface of revolution substantially tangential with the funnel surface and of diameter substantially less than half the corresponding diameter of the chamber, whereby to leave within the annular path of said rollers a substantial reservoir for the materials being mixed, and means for revolving said roller about said funnel axis, in which apparatus the roller has a shaft extension at its upper end and in which a bearing for said shaft extension supports said roller with its surface tangential to the funnel wall and said bearing is mounted for movement toward and away from the funnel wall in parallelism to itself.

References Cited in the file of this patent UNITED STATES PATENTS 

